A vehicle power supplying device that implements resonance to supply charging power through wireless connection from a power supply located outside a vehicle has been proposed in the prior art (refer to patent document 1). The charging system of patent document 1 includes a motor-driven vehicle and a power supplying device. The motor-driven vehicle includes a secondary self-resonance coil (secondary resonance coil), a secondary coil, a rectifier, and an electric storage device. The power supplying device includes a high frequency power supply, a primary coil, and a primary self-resonance coil (primary resonance coil). The distance between the power supplying device and the vehicle changes in accordance with the status of the vehicle (load status, tire pressure, etc.). A change in the distance between the primary self-resonance coil of the power supplying device and the secondary self-resonance coil of the vehicle leads changes in the resonant frequency of the primary self-resonance coil and the secondary self-resonance coil. Patent document 1 thus discloses an adjustment device allowing for adjustment of the resonant frequency of the primary self-resonance coil by changing at least either one of the capacitance or inductance of the primary self-resonance coil. Specifically, the primary self-resonance coil includes a variable capacitor connected between conductive wires. The variable capacitor has a variable capacitance varied by a control signal from a vehicle ECU. By varying the capacitance of the capacitor, the capacitance of the primary self-resonance coil may be varied.
The arrangement of a matching device between the high frequency power supply and the primary coil has also been proposed. When the input impedance of a resonance system changes due to load fluctuation, changes in the distance between the resonance coils, displacement of the resonance coils, and the like, adjustments are performed with the matching device to adjust and match an input impedance of a resonance system and an output impedance of the high frequency power supply. The input impedance of the resonance system is determined by the matching device, the primary coil, the primary resonance coil, the secondary resonance coil, the secondary coil, and the load.